Link Layer Protocol and Error Correction

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Questions and Answers

What is the primary function of the link layer in the network stack?

Encryption and decryption

Routing of packets

Flow control and congestion avoidance

Error detection and correction (correct)

What is the purpose of the EDC (Error Detection and Correction) bits?

To add redundant data for error detection and correction (correct)

To reduce the size of datagrams

To authenticate sender and receiver

To prioritize packets in network transmission

What is the main difference between half-duplex and full-duplex communication?

Half-duplex allows simultaneous transmission and reception, while full-duplex does not

Half-duplex is slower than full-duplex

Half-duplex allows transmission in one direction at a time, while full-duplex allows simultaneous transmission and reception (correct)

Half-duplex is used for wireless networks, while full-duplex is used for wired networks

What is the purpose of the Internet checksum?

To detect errors in transmitted segments Signup and view all the answers

What is the name of the protocol that uses a 32-bit checksum to detect errors in transmitted segments?

UDP Signup and view all the answers

Where is the link layer typically implemented in a network node?

In the network interface card (NIC) Signup and view all the answers

What is the purpose of the Data Link Layer in a network?

To provide error-free transfer of data frames between adjacent nodes Signup and view all the answers

What type of addressing is used in the Data Link Layer?

Physical addressing using MAC addresses Signup and view all the answers

What is the purpose of framing in the Data Link Layer?

To encapsulate datagrams into frames Signup and view all the answers

What is the primary function of the Data Link Layer in relation to error handling?

Error detection and correction Signup and view all the answers

What is the purpose of flow control in the Data Link Layer?

To regulate the transmission rate between adjacent nodes Signup and view all the answers

What is the relationship between the Data Link Layer and the Transport Layer in terms of reliable delivery?

The Transport Layer provides reliable delivery, while the Data Link Layer provides connectionless service Signup and view all the answers

What is the primary purpose of a MAC address?

To get a datagram from one interface to another physically-connected interface Signup and view all the answers

What is the significance of the IEEE in MAC address allocation?

To administer MAC address allocation to ensure uniqueness Signup and view all the answers

What is the advantage of a MAC address being flat?

It allows for portability, allowing a LAN card to be moved from one LAN to another Signup and view all the answers

What is the function of ARP in LAN technologies?

To map IP addresses to LAN addresses Signup and view all the answers

What is the size of a typical MAC address in LAN technologies?

48 bits Signup and view all the answers

What is the purpose of error detection and correction in LAN technologies?

To detect and correct errors in data transmission Signup and view all the answers

Study Notes

Data Link Layer (Layer 2 of OSI)

The data link layer is responsible for transferring datagrams from one node to an adjacent node over a link.
The layer's services include framing, link access, reliable delivery, flow control, and error detection.

Error Detection and Correction

Error detection involves adding error checking bits (redundancy) to data to detect errors.
Error correction involves identifying and correcting bit errors without resorting to retransmission.
Error detection is not 100% reliable, and protocols may miss some errors.

Internet Checksum

The internet checksum is used to detect errors in transmitted segments at the transport layer.
The sender computes the checksum by adding the segment contents as 16-bit integers and storing the value in the UDP checksum field.
The receiver checks if the computed checksum equals the checksum field value; if not, an error is detected.

Link Layer Services

Framing involves encapsulating datagrams into frames, adding headers and trailers.
Link access controls channel access if shared medium.
'Physical addresses' (MAC addresses) are used in frame headers to identify source and destination nodes.

Reliable Delivery

Reliable delivery between adjacent nodes involves ensuring that data is delivered correctly and in the correct order.

Flow Control

Flow control involves pacing between adjacent sending and receiving nodes to prevent data overflow.

LAN Technologies

LAN technologies include Ethernet, hubs, bridges, switches, 802.11, PPP, and ATM.
The data link layer is responsible for addressing in LANs.

LAN Addresses and ARP

LAN addresses (MAC addresses) are used to get datagrams from one interface to another physically-connected interface.
32-bit IP addresses are used to get datagrams to destination IP networks.
LAN addresses are 48-bit addresses burned in the adapter ROM.
MAC addresses are allocated by the IEEE to ensure uniqueness.

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Description

Test your understanding of the link layer protocol, including error correction mechanisms, half-duplex and full-duplex communication, and the role of adapters and frames in data transmission.